Coating for insulation boards



Patented Aug. 8, 1950 COATIKGZFOR'INSULATION BOARDS "HenryZSMoh-l'er, Chicago, Ill.,.ass'ignor to .United'; :Sdatesa-Gypsnmafiempany; Ghicago; 111.5% coriporation ofillinoisr No Drawing. Application July21, 1947, Serial No. 762,543"

Eire present invention relates to improvements in =coatingswas applied: to relatively/porous su-latingwboardaswith especial emphasis upon the application of the mc'oatinigs to .theinsulation boardat thatsta'ge of its manufactereawherelitiis stiiliwet, so thati'the drying of .the-bc'arduandvof the coating can take place simultaneously;

Attempts have been madeitoooitlaispbut itw-as soon discovered: that: unless special 1 precautions -were: taken lay the incorporation of #the" stepsolt the. present "invention;as."hereinbelowwmore lfuizly stated, thecoatings would *he uneven and of unsightl-y, blotch'ed'appearance. This'was notice-- abl'e evenwith white coatings, containingra-starch ..vehicle andna water.-dispersedfclaypand waspar vticularly marked 'tin'ted an'd ooloredwoatings; such as are usually-"applied td insulation board that is intended-as the interior surface of houses; In such cases it was also found 'thatrlit was *virtually impossible" to maintain' a un orm shade or color over an extended period of 'ti'me; =even-though the same batch s01 icoatingficom oosi- .131011 was *u'sedvduringthe entire'runi ltfwas .iurther discoveredtha't this irregularity in appearance was occasioned by whaamayiprop- :erly b'e termed'the migrationentire various components of the coating composition; which phenomenon is- :markedly accentuated when the coating is applied to "the wet insalation'hoard. This migration is believed to be causedb'y:

(1) Seepage of water 'soliiblematerialsvin the wet insulating board mat to thesurfaceudnring the drying operation;

(2) Migration of 1a starch ifilm itOthEfSlITlfZICB :of the coating:

(3) The rising-of pigment'particl'es *lto thetsur; iface together with the-.zniigra-tion :of the starch.

In the case of-light coloredcoatings; such-:as white orv ivory tints; causes Land #2. are "believed to account for the major share of the migration; while in thecase of thewdarkerucolors; :theetliird cause appears $170 be .the -mosttimeortanti con tributingiactor; Thecdegreeto:whichrmigration .a-iiects :the final :coler of thescoatinjg-maymbetde termined by-preparing-1tvvo coatingsicontaining thesamevquantitiesxoi xcolored pigments; ronezof z ion-the thicknessroithe coatingxappliect; .inzothe'r words, the'ithicker the: coating, thewgreater will bathe difference .imcolor. Another-factor is the perneritage of water ii'ntheacoating; :asthis also: in fluencesfthe amount o'f'migrati'on'.

Migration in starch coatingsrtlius idep'ends 1115i"- marily :upon :two. factors:

(1*) :Theramonntzoi waterrpreserrtrinethetcoating which; in turn; determines the rateni drying-after its application towthe surface of the board. @1195 viousiiy q the longer? the ;drying.1ft'ime; the; :rnore starch (and pigment particles carried thereby) 'can'riseto'thesurface.

("2) The-thickness Ufthe' coating film likewise produces a disturbing 'eiTect." Whena thin film of *co ating-is 'app'liedtoth'e board; only relatively small quantities of'starch and 'pigmentwan r'ise to "the surface'of thecoat'rng'; while; conversely, when a heavier" coat is applied; larger "amounts of starch andpigment can migrate during the dryin Operation.-

It might -.be believed. that .mostof thesedifia oultiesecould-oe resolved bythe-,propencontnobof uniformity in the acoati-n-g :cornpositions and ace curacy in their application, but th-iszisdefeated by the. fact that the--r-iniierent and wcharacteristic texture rofrtheeinsulating board :is :such as-to we; clude the application of an evenwcoatinga-over every portion of its surface. When rise-considered that insulation. board is made. by; fenntinuously filtering out a dilutesuspension of more or; less: heavily sized fibers-ion a filter wheelrsuch asithat. of an Oliver type -oi.'board-.-torming; .mae chine; and that lthe resultant .wet hoard isathen compressed between absorbent? f elts. which are pressed against theboardby l?O1'11-S,*:lt williat oncecbe evidentthat eittcould notpessibiy have :a snfficiently smoothsurface to pgerrn it-thelapplicae tiomof .an entirely even coating. Theboardl-wil-l .alsohe-unequaily absorbent :on its surfaoe-, .-a-nd \will: contain low spots as --weil. Its-relatively rough textureralso precludes .thevuse of a doctor blade, and the. coating must he :appliedaby.zneams iwhiclifidovnottea-r up the-suriaceao-f therboarld. Usually; such coating-s are applied vby a: 33001 :and roller: method, a pool-of the COG/ting composition being maintained just .aheadof aspreading rol-ler which controls; within'the limits as. just:-.defined; itheathickness :of the-coating. While thGwd-iSllZlHCB of the-roller from the highest "IlQllliEBlS-Df the board-can be: accurately 'adjusted,;.'yet .thea'low spots will-unavoidably bezprovitled withvatthicker coating.

'Theapresent invention has for. its primary oiie- ;ject theaproduction .oi coatingsaomstill oughly gelatinized starch solution.

sulation boards, which coatings will dry uniformly to an even and pleasing appearing surface, which can be used for decorative purposes, without requiring recoating or painting by the user.

A further object is to provide a coating so constituted that migration of the vehicle and the pigments and fillers therein will be sufficiently repressed, or'totally avoided, particularly when the coating is rapidly dried at temperatures above atmospheric, to the effect that uniform coatings can be secured.

Further objects of the invention will appear from the more detailed description to follow.

The novel feature of the present invention is the incorporation with a vehicle consisting of starch, and in which pigments, fillers and colors are suspended, of a suitable amount of a material from the group consisting of the butyl alcohols and tributyl phosphates, which materials will prevent the migration of the starch vehicle and of the pigments, this being particularly true when the drying is effected rapidly, as at temperatures above atmospheric. The additive materials may be incorporated with the coating composition at almost any stage of its manufacture, but preferably after it has been compounded.

A suitable composition may consist of the following ingredients, in about the proportions given (which are the amounts present in the finished composition in the form in which it is ready for application to the still wet insulating board) Parts by weight Starch (gelatinized) 25 Clay 128 Ground mica 40 Tetrasodium pyrophosphate 0.6 Pigments 20 A tributyl phosphate 5-20 Water 150-250 One of the butyl alcohols may be substituted for the tributyl phosphate, such as normal, secondary, tertiary or iso-butyl alcohol. The butyl radical in the phosphate may be any one of the four known butyl groups.

If butyl alcohol is used, it will require from 40 to 80 parts thereof instead of the 5 to 20 of the tributyl phosphate.

The following is an operative example of one method of successfully compounding the above coating composition:

100 pounds of a thin-boiling starch (for instance a mixture of pearl starch and oxidized starch) are suspended in 640 pounds of water to form a starch milk, which is then cooked at about 200 F. for about minutes to produce a thor- In another tank containing 720 pounds of water, '700 pounds of white coating clay and 250 pounds of finely ground mica, of the type used in making papercoating compositions, are added, being dispersed in the Water by the aid of 3.5 pounds of tetrasodium pyrophosphate as a deflocculating agent, so that a smooth suspension of the clay and the mica will result. The previously made starch solution is now combined with the clay and mica suspension and the mixture stirred until uniform. If a colored coating is to be made, the colors are first blended with the clay and mica suspension prior to the addition of the starch solution.

There is then added the calculated amount of either the tributyl phosphate or the butyl alcohol, based upon the proportions above given, and the mixture is stirred until uniform. As both the tributyl phosphate and the butyl alcohol are liquids, this is readily accomplished. Finally, enough water is added to bring the volume of the composition to 116 gallons.

The coating thus prepared is then applied to the wet insulation board, preferably at a time when it is still on the forming-machine and before the continuous ribbon of wet insulation board is cut into individual board lengths. The coating method may be any that is now in use. although the pool and roller method is the preferred manner of applying the composition. A

very effective way to apply the coating composition is to pour it onto the moving wet board, through a pipe provided with numerous perforations, directly ahead of a suitable distributing roller, so that a more or less constant pool of coating composition will be built up ahead of the roller. The coating composition may be supplied from a suitably elevated supply tank, running to the perforated pipe by gravity, or it may be pumped from a lower elevation. Such means and methods of coating are very well known in the art, and hence require no illustration or further explanation as they will be fully understood by those skilled in the art. The board then proceeds into a dryer, in which it, as well as the coating, is dried.

The choice of fillers and pigments is, obviously, quite large, depending upon the color of the coating. The clay and mica are both fillers, although in the case of white or light-colored coating compositions, they may also play the dual role of pigments. Other white pigments such as titanium dioxide (preferably on barium sulfate), satin-white, zinc oxide, etc., may also be used. Colored pigments may include chromium oxide, cadmium sulfide, ultramarine and various colorlakes, lamp-black, and the like. Hence in the subjoined claims, the term pigment-fillers is used as a collective designation of pigments and fillers.

Obvious equivalents, and mixing techniques known to the art, are to be construed as within the scope of the present invention for which applicant claims:

1. A liquid coating composition suitable for application to wet insulating board during its process of manufacture consisting essentially of an aqueous gelatinized starch vehicle, pigmentfillers, and an amount of tributyl phosphate equal to from about 20% to about by weight, calculated on the starch in the composition.

2. A liquid coating composition suitable for application to wet insulating board during its process of manufacture, consisting essentially of pigment-fillers, water, and a binder which latter consists essentially of gelatinized starch and from about 1 to about 4 parts by weight of a tributyl phosphate for each 5 parts by weight of said starch.

3. A liquid aqueous coating composition suitable for application to wet insulating board during its process of manufacture containing water, pigments and a starchy binder which latter consists essentially of gelatinized starch and a tributyl phosphate, the relationship of the starch and tributyl phosphate (on a dry weight basis) being about as 5 of starch to from about 1 to 4 of said tributyl phosphate.

4. A liquid coating composition suitable for application to wet insulating board during its process of manufacture containing water, pigments and a starchy binder which latter consists essentially of about 25 parts by weight of starch and about 5 to about 20 parts by weight of a tributyl phosphate, the starch being In the UNITED STATES PATENTS gelatin'i'z'ed condition. Numb N D t 5. A' gliquidcoating composition suitable for ap- 1 g ig Oct 61929 plicatib'n to wet insulating bog i'd during its proc- 1827083 Harvey 1931 ass of nufacture COHSiStiDgQLQSSBIItiaHY of about 5 2185859 Massey 1940 the Ew ingredients" li by Weight 2:229:620 Bradner IIIIII Jan. 21: 1941 Starch; (:e1i ajltinized) 1 25 2,287,161 Ball June 23, 1942 lei-s 188 2,374,676 Gardner May 1, 1945 hosphate 5 to 20 I 2,378,113 Van De Carr June 12, 1945 15016 250 10 2,388,526 Craig Nov. 6, 1945 f HENRY z. MOHRER. OTHER REFERENCES PREFERENCES Kerr: Chemistry and Industry of Starch,"

i pages 356, 357, and 452, published by Academic The following references are of record in the 15 press, Inc" New York, (1944) tile or this patent; 

1. A LIQUID COATING COMPOSITION SUITABLE FOR APPLICAITON TO WET INSULATING BOARD DURING ITS PROCESS OF MANUFACTURE CONSISTING ESSENTIALLY OF AN AQUEOUS GELATINIZED STARCH VEHICLE, PIGMENTFILLERS, AND AN AMOUNT OF TRIBUTYL PHOSPHATE EQUAL TO FROM ABOUT 20% TO ABOUT 80% BY WEIGHT, AS CALCULATED ON THE STARCH IN THE COMPOSITION. 